A quietly majestic survey of the hard-won successes and instructive failures of the American environmental movement.

“Earth Days” is a quietly majestic survey of the hard-won successes and instructive failures of the American environmental movement. Avoiding the alarmist tone characteristic of many ecologically themed documentaries, Robert Stone’s latest opus is a moving, elegiac, deeply contemplative work that leaves the viewer not with a save-the-world checklist, but rather a spirit of hopeful reflection. Classy presentation, breathtaking archival footage and authoritative voices from all corners of the movement suggest a very sustainable smallscreen career, though theatrical bookings are also warranted. Pic will air on PBS in April 2010 to commemorate the 40th anniversary of Earth Day.

A dense weave of images, voices and music, “Earth Days” is, above all, a chronicle of shifting generational attitudes: the spirit of conservation that prevailed during the Great Depression; the sense of unlimited abundance and national invincibility that accompanied the postwar economic boom (clips from ’50s car commercials and family sitcoms abound); the ’60s counterculture’s attempts to raise public awareness of global pollution and depletion (leading to the first Earth Day on April 22, 1970); and the unfortunate reduction of the environment to a polarizing political issue over the past three decades.

Recounting these trends with varying degrees of affection, nostalgia and world-weary regret are nine pioneering environmentalists, introduced with monikers such as “the Radical” (journalist-ecologist Stephanie Mills, known for her views on human overpopulation) and “the Conservationist” (Stewart Udall, who used his 1961-69 tenure as secretary of the interior to pass clean-air and clean-water acts and preserve endangered wildlife).

Pic acknowledges the impact of Rachel Carson’s galvanizing (and at the time, much-maligned) 1962 bestseller “Silent Spring,” which laid the groundwork for the entire movement with its critique of widespread pesticide use, as well as Paul Ehrlich’s “The Population Bomb.”

Hippie astronaut Rusty Schweickart reminisces about the 1969 Apollo 9 lunar mission, inspiring the film’s most rhapsodic passage: a selection of photos of the Earth from outer space that serve as a powerful reminder of the planet’s beauty as well as its fragility.

While “Earth Days” is a movie about activists, it is not, strictly speaking, an activist movie. It’s more ruminative than didactic: The way the voices bob and weave throughout, the near-subliminal layering of the images, the relative absence of charts, diagrams and statistics, and the stirring refrain of Michael Giacchino’s score make for a somewhat languid but ultimately hypnotic experience that rewards close viewer attention.

Stone (“Oswald’s Ghost,” “Guerrilla: The Taking of Patty Hearst”) isn’t one to lecture his audience, yet the ironies are there for the taking. Hippies may have scorned technology as the root of all environmental evil, but, as biologist Stewart Brand rightly point outs, technology can also solve problems — and often solve them more effectively than human efforts to create sweeping social or political change.

That’s not the only time the film favors a clear-eyed, practical approach over a naively idealistic one: President Nixon gets more credit here for his (politically motivated) efforts, which included the creation of the Environmental Protection Agency in 1970, than President Carter does for his sincere but misguided attempts to win over Americans to the cause by emphasizing the need for individual sacrifice.

“We lost 30 years,” sustainability expert Hunter Lovins says wistfully of the political deadlock that set in with the Reagan administration. But while its tone is occasionally steeped in the bitter wisdom of hindsight, “Earth Days” manages to conclude on an optimistic note, holding out hope, no less than its subjects, for the future.

Tech credits are superb.

Earth Days

Production

An American Experience Films presentation. Produced by Robert Stone. Executive producer, Mark Samels. Directed, written by Robert Stone.